MIDLAND, MI — An arm of the World Health Organization has listed a widely-used herbicide made by The Dow Chemical Co. and other companies among "possible" human carcinogens.

Officials at Midland-based Dow say the classification is "inconsistent with government findings" in the United States and many other countries.

Officials with the International Agency for Research on Cancer, a Lyon, France-based arm of the World Health Organization classified 2,4-dichlorophenoxyacetic acid, also known as 2,4-D, as "possibly carcinogenic to humans."

Dow spokeswoman Rachelle Schikorra said "2,4-D is a molecule manufactured and used by several companies, and is not specific to Dow or Dow products."

Dow sells a product containing the herbicide called Frontline, according to the Dow AgroSciences website.

The herbicide has been widely used on crops and pastures around the world for 70 years.

"The herbicide 2,4-D was classified as possibly carcinogenic to humans (Group 2B), based on inadequate evidence in humans and limited evidence in experimental animals," the IARC press release states.

"There is strong evidence that 2,4-D induces oxidative stress, a mechanism that can operate in humans, and moderate evidence that 2,4-D causes immunosuppression, based on in vivo and in vitro studies. However, epidemiological studies did not find strong or consistent increases in risk of NHL or other cancers in relation to 2,4-D exposure."

Dow officials in a press release said "the classification of the herbicide 2,4-D by the International Agency for Research on Cancer (IARC) is inconsistent with government findings in nearly 100 countries, including the U.S., Canada, U.K., Germany, France, Japan, Brazil and China, which have for decades affirmed the safety of 2,4-D when used according to approved labeling."

"Government reviews were based on rigorous hazard and risk evaluations of more than 4,000 scientific studies. In sharp contrast to the government reviews, IARC, an agency of the United Nations World Health Organization (WHO), reviews an incomplete set of information to focus solely on whether a substance or activity could be a carcinogen, not whether it is a carcinogen when used under real-world circumstances," Dow officials said in the release.

John Cuffe, Global Regulatory Sciences and Regulatory Affairs, Dow AgroSciences, said "no herbicide has been more thoroughly studied and no national regulatory body in the world considers 2,4-D a carcinogen."

"In fact, IARC stated that there is 'inadequate evidence' for human carcinogenicity," Cuffe's statement continued. "IARC's findings on 2,4-D are not the last word even within the WHO, whose JMPR (Joint Meeting on Pesticide Residues) does not consider the handling and use of approved 2,4-D herbicides to pose a cancer risk."